Discharge tube



March 24, 1936.A

` wif J, BRulJNEs ET A1.

DISCHARGE TUBE Filed Aug. 4, 1951.

w/Cfeng ami marca] Patented` Mar. 24, 1936 PATENT OFFICE DISCHARGE TUBE Johannes Bruijnes, Ekk hannes Gijsbertus Wi Netherlands, assigno lampenfabrieken, Ei

In the Netherlands 1 Claim. (Cl.

This invention consists in part of an improveent in the arc discharge tube disclosed in the copending application of Johannes Bruijnes, Serial Number 736,343, led September 6, 1924, and is a continuation in part of our copending application Serial Number 162,896, led January 22, 1927. The invention consists primarily in reducing to a minimum the difference between the ignition potential and running potential of an electric discharge tube, more particularly of the arc discharge type. The invention is also concerned with the production of an arc discharge tube having a lower potential drop across the tube during the normal operation thereof than has hitherto been possible with similar tubes of normal commercial life, and at the same time is directed to the production of such a tube in which the current ow through the tube starts at an earlier point during the desired voltage half Wave than has hitherto been possible with such tubes. In its broadest aspect, the invention resulting in the advantages above pointed out, consists in adding in the tube a small quantity of suitable vapor, more particularly mercury vapor, and in an improved form of the invention there is added to a tube according to the aforementioned Bruijnes application, that is, a tube having a Wehnelt cathode, electrodes closely spaced with respect to each other, and a gas filling of monatomic gas preferably argon, a small quantity of mercury adapted to be readily vaporized.

Another object is to produce a new tube having a low voltage drop across the tube during the normal operation thereof, without diminution in the commercial life of the tube, which is of the same order of magnitude as the present day radio tubes.

Another object is to produce an arc discharge tube which has low voltage starting characteristics approximating the running characteristics of the tube.

Another object is to discharge tube havin sistance.

Another object is to produce an arc discharge tube having low voltage starting characteristics approximating the operating characteristics, andy in which the operating efficiency is increased considerably over the hitherto known tubes.

Another object is to produce an arc discharge l tube in which the starting characteristics are so designed that the usual ballast resistance is either entirely avoided or considerably decreased in ohmic value. y

4 Another object is to produce a newrectifyingproduce a new type of arc g a decreased internal relhelm Mulder,

o Oosterhuis, and Jo- Eindhoven,

to N. V. Philips Gloeindhoven, Netherlands Application August 4, 1931 Serial No. 555,121 January 29, 1926 tube in which the curre desired volta known tubes.

Another object is to produce a tube having a lling of monatomic gas such as argon, together with mercury vapor, and having a Wehnelt cathode, the electrodes being closely spaced with respect to each other.

Yet another object is to low voltage starting char ing the running characteristics of the tube and in which the space charge produced during operation is substantially entirely removed.

Other objects will appear as the specification advances.

In the drawing formin tion Fig. 1 is a side el embodying our inven Fig. 2 is a diagram embodying our inve therefor.

Fig. 3 is a da erating currents tube according pared nt starts earlier in the ge half cycle than in the hitherto produce a tube having acteristics approximat- 10 g part of this specificaevation of a discharge tube tion.

showing a full-wave rectier ntion and the electric circuits gram showing for different opthe voltage drop across a rectier to our present invention com- Figs. 4 and 5 are diagrams showing oscillograms of the current flow through rectier tubes made in accordance with the above Bruijnes inventionv and according to the present invention respectively.

One form of our invention is illustrated by way of example in the accompanying drawing,

e is shown a tube l of glass or simto which a reentrant tube 2 may y sealed. Leading-in wires 3 and s sealed to a cathode 5, preferably elt or oxide-coated type, in addition -in wire 6 of the anode 1. In any esired that the cathode will copiously ons at low cathode temperatures, in void vaporization of the cathode material, and to increase the power consumption efciency of the tube. The leading-in wires above referred to are all shown as sealed to the press at the end of the reentrant tube. The leading-in wires in the present instance are connected to contact pins 8 shown as mounted ilar material be hermeticall 4 are shown a of the Wehn to a leading event it is d emit electr order toV a gas, preferably argon, bring about the desired cury vapor.

be spaced at a distance from each other approximating the mean free path of the electrons in the vapor at the selected pressure thereof.

In a particular example, for instance, the electrodes may be placed at a distance approximating 10 mm., while the argon is present at a pressure of approximately 4 mm., the mercury vapor having a pressure of approximately 100 microns during operation. Objectionable occlusion of the gas and vapor in the tube walls is prevented, due to the fact that the potential drop across the tube is very low so that the positive ions are not accelerated to such an extent that they cause disintegration of the electrodes.

Whereas in previous discharge tubes the disintegrating parts when deposited on the wall of the bulb, occluded the gas-molecules. It is of course understood that substances other than mercury could be employed, perhaps with not the same desirable results. Such materials might be for instance, natriurn, caesium, rubidium, potassiurn, the criterion being that the added vapor lonizes at a lower tension than does the rare gas. The added vapor preferably should have a pressure such that the atmosphere within the tube will substantially always be saturated therewith, the desired pressure preferably lying between 1 mm. and 20 mm. and generally being of the order of 4 mm.

When such tube is employed, experience has shown that the presence of the mercury vapor operates to materially decrease the voltage which must be impressed across the tube terminals in order to ignite the same, so that it more closely approximates the running voltage of the tube. By this, it is possible to materially decrease the ohmic value of thel ballast resistance which has hitherto been employed in automatic installations, while in the case of manually operated installations,4the careful control of the starting and running voltages is not nearly so essential as has hitherto been the case.

Experience has shown that the efficiency of a ballast resistance installation employing the present tube is approximately 30% greater than when tubes of the prior art are employed.

Actual comparative tests have been carried out with the tube according to the present invention, as compared with a tube according to the copending application Ser. No. 736,343.

The data were measured by placing the tubes in a rectlfying device, the diagram of connections of which is shown in Figure 2.

Herein, I0 indicates a transformer whose primary winding II has a resistance of 60 Q, and is connected to a 220 volt network. The portions I2 and I3 of the secondary winding each have a resistance of 0.75 S2, and give a voltage of 16 v. The total voltage of the secondary winding I4 for feeding the cathode I5 of the tube I6 is 2 volts.

One side of the direct current load I1, formed by a battery, is connected to the middle of the secondary winding I2, I3, the other side to the middle of the winding I4.

Y The tube IB has two anodes I8 and I9.

From the diagram of Fig. 2 it may be seen immediately, that both half waves of the alternating current are rectified.

The compared tubes each contained two anodes, at a distance apart of 14 mm.,an oxidecathode being placed in the middle between these anodes. They contained an argon lling with a pressure of 16 mm. The height of the tubes was mm., the diameter 32 nim. The only difference between the two tubes was, that one of them contained a drop of mercury. The strength of the rectied current was measured for each tube with three different direct current loads (by changing the number of cells of the battery I1).

The results were as follows:

Strength of the current tgoltaage of e a ery charged by Tubecon- Tgifgn the rectifier talnmg argon and argon mercury 6.2 volts 0.88 amp. 1.16 amp. 4.2 volts 1.12 amp. 1.32 amp. 2.1 volts 1.28 amp. 1.44 amp.

In the left hand column the voltage across the battery or load is given, while in the other columns the current flow given. It will be noted that in each instance the current iiowing through the argon mercury filling tube (that is, applicants tube) is greater than that through the other tube. This indicates conclusively that the voltage drop through the tube according to applicants invention is much lower than in the case of the other two tubes, in View of the negative volt-ampere characteristics of arc discharge tubes. It is of course of great advantage from the standpoint of economy and eiciency to decrease the running voltage of the arc discharge tubes while retaining the essential long commercial life.

That the decreased terminal voltage across the tube is actually produced is clearly evident from comparative measurements obtained during the tests, and as indicated in the chart given below.

The data were measured using the sarne tubes, with which the above described comparative tests as to charging current were taken.

For different currents the voltage drop between an anode and the cathode was measured.

Fig; 3 shows these data in characteristic curves. They show that the ignition voltage of the tube containing only argon corresponds with the ionization voltage of the argon (15.7 v.) whereas the ignition voltage with the tube, containing argon and mercury is only 10.5 v. This is a lowering of the ignition voltage of 32%.

Further the running voltage is also materially lower.

Life tests indicate and substantiate the above allegation of long commercial life. 'I'his is shown for instance by the following test.

Five tubes of the kind described, containing argon and mercury, were each placed in circuit in a rectifying device, the direct current load being 1.35 amp.

The cathode was an oxide Vcathode with barium oxide.

They were switched After more than a year,

in 0n Nov. '7th, 1927. 0n NOV. 17th, 1928 they through the tube is also were switched off. Each of the tubes operated for more than 8,000 hours, and none of them showed any failure.

We remark that the circumstances were not chosen as favourable as possible, for in this case tubes were used having an argon pressure of only 4 mm. It is generally known that with higher gas pressures a higher life may be obtained.

Other tests have shown that the life of the tube may reach 14,000 hours.

A still further advantage of the tube of the type described above is that the current flow through the tube during the desired voltage half ing in applicants device as compared with that of the prior art is shown in Figures 4 and 5 by means of oscillograms.

The oscillograms relate to the same tubes for which the currents at diierent loads and the terminal voltages across the tube were measured.

Fig. 4 relates to the tube containing only argon, Fig. 5 to the tube containing argon and mercury. The curves eb represent the course of the terthe rectifier. In the oscillograms g are the points where the discharge starts.

been employed as the basis of the calculations cited above. It has been pointed out that the preferred form of tube comprises a Wehnelt cathode in combination with the desired electrode spacing and desired pressure of gas-lling. A Wehnelt cathode is employed because of the desirability, and in fact, necessity of obtaining the necessary emission of carrier electrons from the cathode at a low temperature. Not only does the copious emission of electrons at a low pressure increase the overall eiciency of the tube, but

it has been found that the high temperature necessary to expel the desired number of electrons from a refractory metal cathode results in detrimental vaporization of the cathode material.

'I'he same is the case when the cathode is of the thoriated tungsten type. In all such tubes containing a refractory metal cathode the vaporization of the cathode makes high pressures It is not yet fully clear to which phenomenon the extraordinary low ignition and running voltage of a tube with the gas lling described is due. Probably part of the effect is caused by the fact, that the electrons, starting from the Wehnelt of the monatomic gas as soon as these electrons have traversed the excitation voltage of this gas.

For argon e. g. such an excitation voltage is 11.9 v.

mercury atom). It is not possible for the mercury atoms to be ionized immediately by the electrons, the mercury being present in too small a percentage.

The excitation of the atoms of the monatomic gas as soon as an electron has traversed an excitation voltage and the ionization of the mercury vapour which is a consequence thereof means a very eiiicient utilization of the potential diiTerence between the electrodes.

It is obvious that after the invention has been once disclosed numerous modifications adaptations will readily occur to those skilled in the art. Accordingly, it is intended that our invention be limited only by the scope of the appended claim.

What we claim isri An electric discharge tube comprising a Wehnelt cathode, an anode, said cathode and anode ly 100 microns in operation.

JOHANNES BRUIJNES. EKKO OOSTERHUIS. JOHANNES GIJSBERTUS WILHELM MULDER. 

